1. Field
Example embodiments relate to a teaching and playback method for a robot having at least one redundancy resolution, particularly a robot with an elbow having an offset, using a redundancy resolution parameter determined in conjunction with a joint structure.
2. Description of the Related Art
A teaching and playback algorithm based on Inverse Kinematics (IK) is used for control of an industrial robot. A robot arm such as a 7-axis manipulator has recently emerged to mimic the natural movement of the human arm.
In general, differential IK and analytical IK are used as IK. It is known that analytical IK is restrictively applicable to a Spherical-Regulated-Spherical (S-R-S) manipulator which allows for geometric and algebraic analyses.
There are basically six coordinate system parameters for an end-effector of a robot, and one or more redundancy resolution parameters are defined for posture control. An arm angle is used as a redundancy resolution parameter. The arm angle is defined as an angle between a reference plane formed by a reference vector and a shoulder and wrist of the robot and an arm plane formed by the shoulder, elbow, and wrist of the robot.
In differential IK, the arm angle is used for Extended Jacobian as a parameter of a cost function, whereas in analytical IK, the arm angle is used as a parameter of operational space.
Even though the robot has the coordinate system parameters for the end-effector and seven teaching values as arm angles, one arm angle may represent two shoulder postures at the same time. Therefore, there is a limit on the playback function of the robot to return to the same position and posture all the time.